One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,4)(5,6)(7,12)(8,10)(9,11)(13,14,17,21)(15,22,25,28)(16,20,18,26)(19,27,23,24)(2,4)(7,8)(10,12)(13,14)(15,23)(16,26)(17,21)(18,20)(19,25)(22,27)(24,28) involution — undirected(5,7,9,8)(6,10,11,12)(13,15,18,24,17,25,16,27)(14,19,20,22,21,23,26,28)(5,8,9,7)(6,10,11,12)(13,16,17,18)(14,20,21,26)(15,24,25,27)(19,28,23,22)(6,11)(10,12)(14,21)(19,23)(20,26)(22,28) involution — undirectedA Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.